Apparatus for developing continuous electrophotographic photosensitive web material

ABSTRACT

An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural developing electrodes which are larger in dimension than the latent image area formed on the photosensitive material and which are arranged along the periphery of the support rollers so as to be in facing relationship with slight spacing therebetween with the continuous electrophotographic photosensitive web material to be wound the support drums at least over the length of the latent image area with the rear side thereof towards the drums, a means for supplying liquid developer into the space between the developing electrodes and the photosensitive material, and advancing the photosensitive material intermittently so as to bring all the latent image areas in the developing section into facing relationship with developing electrodes respectively when the photosensitive material is brought to standstill.

United States Patent [191 Sato et al.

[30] Foreign Application Priority Data July 3, 1970 Japan 45-58130 [52] US. Cl 118/637, 117/37 LE, ll8/DIG. 23 [51] Int. Cl G03g 13/00 [58] Field of Search 118/637, DIG. 23; 355/10;

95/89 L; 117/37 LX [56] References Cited UNITED STATES PATENTS 3,186,326 6/1965 Schmidt l. 95/94 3,556,050 l/l97l Trachtenberg 118/637 3,227,549 l/l966 Ullrich, Jr. et al 96/1 3,307,458 3/1967 Hunstiger et a1. 95/1.7 3,415,223 12/1968 Zweig v l 118/637 3,601,092 8/1971 Toyokazu 118/637 3,577,259 5/1971 Sato 118/637 FOREIGN PATENTS OR APPLICATIONS 85,131 4/1957 Netherlands ll8/DIG. 23

[ Mar. 12, 1974 Primary ExaminerMervin Stein Assistant Examiner-Leo Millstein Attorney, Agent, or Firm-Gerald J. Ferguson, Jr.; Joseph J. Baker; .1. T Martin [57] ABSTRACT An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural developing electrodes which are larger in dimension than the latent image area formed on the photosensitive material and which are arranged along the periphery of the support rollers so as to be in facing relationship with slight spacing therebetween with the continuous electrophotographic photosensitive web material to be wound the support drums at least over the length of the latent image area with the rear side thereof towards the drums, a means for supplying liquid developer into the space between the developing electrodes and the photosensitive material, and advancing the photosensitive material intermittently so as to bring all the latent imageareas in the developing sectioninto facing relationship with developing electrodes respectively when the photosensitive material is brought to standstill.

4 Claims, 6 Drawing Figures PATENTEBIAR 12 m4 SHEET 1 BF 2 INVENTORS, MASAMICHI SATO OSAMU FUKUSHIMA SEIJI MATSUMOTO ATTORNEYS,

PATENTEMR 12 m4 SHEET 2 OF 2 PEG. 6

INVENTORS, MASAMICHI SATO OSAMU FUKUSHIMA SEIJI MATSUMOTO BY W o" M ATTORNEY-S.

3 APPARATUS FOR DEVELOPING CONTINUOUS ELECTROPHOTOGRAPHIC PHOTOSENSITIVE WEB MATERIAL This invention relates to an apparatus for liquid development of continuous electrophotographic photosensitive web material, and particularly to an apparatus I capable of providing uniform images free from uneven development under intermittent advancement. Also this invention is to provide an apparatus capable of extending the length of developing section without using very large dimension of the apparatus, of obtaining sufficiently long developing time and of enhancing the effect of developing electrode thereby enabling to obtain continuous tone image of extremely high quality exactl'y corresponding to the electrostatic charge distribution of latent image.

In general the electrophotographic image by liquid development can be prepared by uniformly charging electrostatically by means for exampleof corona discharge an electrophotographic photographic layer provided on a suitable electroconductive support material thereby endowing photosensitivity to said layer, subjecting said layer to imagewise exposure of original pattern to be reproduced thereby modulating said uniform electrostatic charge corresponding to said pattern (hereinafter referred to as electrostatic latent image), bringing said layer into contact with liquid developer consisting of colored charged fine particles (hereinafter referred to as toner) dispersed in an electroinsulative liquid thereby depositing said colored charged fine particles onto said electrostatic latent image selectively to obtain visible image. It is extremely. difficult, however, to obtain developed image exactly corresponding to the latent image. Uneven development is frequently observable particularly in case of forming images at fixed intervals on a continuous electrophotographic web material. This invention is to provide an apparatus capable of forming images without uneven development and exactly corresponding to the latent image even in such case of forming images successively on said web material.

ln electrophotographic processes the use of developer electrode is common in order to suppress socalled edge effect (a phenomenon of preferential development on the peripheral portion with insufficiently low density in the central portion of a wide image area which should be developed into an-uniform density) and halo (a phenomenon of excessively low density appearing in the peripheral portion of low density area adjacent to high density area) which are inherent to electrophot'ography. Said developing electrode generally consists of an electroconductive counter plate provided parallel to the latent image surface in order to increase the number of flux of electric force and to absorb said flux thereby generating the distribution of electric field exactly corresponding to the distribution of electrostatic charge. It is generally accepted that the effect of developing electrode becomes stronger and consequently the edge effect and halo become more suppressed as the distance between the developing electrode and the latent image surface (hereinafter referred to as developing electrode distance) decreases. It is practically difficult, however, to maintain said developing electrode distance over the whole image area, and local fluctuation of said distance will directly result in unevenness in developed density particularly when a small developing electrode distance is employed. Such local fluctuations are inevitably unavoidable since the latent image surface and the developing electrode cannot be ideally flat. Thus, the unevenness in developed density isenhanced even by a slight fluctuation of said distance if said distance is made smaller in order to obtain an image exactly corresponding to the charge distribution of latent image and being almost free from edge effect and halo. This problem becomes more vivid when the development is carried out while the'latent image surface and the developing electrode are kept in a mutually still relationship. In the apparatus according to this invention, each image is made to face at least two developing electodes until the completion of development under supply of fresh liquid developer for each developing electrude thereby to cancel the unevenness generated by each developing electrode.

More specifically this invention is to provide an apparatus for developing intermittently advanced photosensitive continuous web material to form images successively at a determined interval on said web material, which comprises developing an image on said web material under facing relationship with a developing electrode, then advancing said web material by the length of one frame thereby bringing said image into facing relationship with a second developing electrode, further developing said image under facing relationship with said second developing electrode, thus completing the development after facing plural developing elec trodes thereby obtaining developed image free from edge effect and halo as well as unevenness in developed density.

Thus, the apparatus according to this invention is particularly suitable for combining with an electrophotographic apparatus in which the photosensitive web material is advanced intermittently and subjected to imagewise exposure while it is kept in standstill, but it is also naturallypossible to combine this developing apparatus according to this invention with an electrophotographic apparatus in which the exposure is carried out on a photosensitive web material advanced continuously.

In case of exposing different original patterns'successively on a photosensitive web material, however, it is ordinary necessary to modify exposing condition for each original. Such modification for each frame is rather difficult to realize in case of exposure under continuous advancement. Thus, still exposure with intermittent advancement of photosensitive web material is more advantageous when modification of exposure condition for each frame is required.- On the other hand, the already known apparatus for developing continuous electrophotographic photosensitive web material usually employs developing under continuous advancement of web material. Consequently if intermittent exposure method is employed combined with such known apparatus, it becomes necessary to incorporate a mechanism for converting intermittent movement into continuous movement.

This invention is to remove such drawback, and to provide an apparatus for developing said web material under intermittent advancement in the developing section.

BRIEF EXPLANATION OF DRAWINGS FIG. 1 is a schematic cross-sectional side view of an electrophotographic apparatus for forming images on a continuous electrophotographic photosensitive web material provided with the developing apparatus according to this invention.

FIG. 2 is a schematic cross-sectional side view of another example embodying this invention.

FIG. 3 and FIG. 4 are perspective views of guide roller to be employed in the apparatus of FIG. R.

FIG. 5 is a perspective view of dancer roller to be employed in the apparatus embodying this invention.

FIG. 6 is a perspective view of a support drum.

DETAILED DESCRIPTION OF INVENTION This invention will be further clarified by the following description with reference to the attached drawings. In FIG. ll showing cross-sectional side view of an example embodying this invention represented are a continuous electrophotographic photosensitive material (hereinafter referred to as photosensitive material) I in rolled state with the photosensitive layer thereof outward, a pair of pinch rollers 2 and 3 made for example of rubber rollers for advancing said photosensitive material by a determined amount, a dancer roller l shaped as shown in FIG. 5 to hold and advance said photosensitive material between the flanges 50 in order to give a determined tension to said photosensitive material thereby preventing the slackening of said photosensitive material, and a pinch roller 5 made of elastic material such as rubber to press said photosensitive material against a drum 6, which determines the amount of advancement of said photosensitive material for realizing the registration thereof in the longitudinal direction, by means for example of providing sprocket on the end portions of said drum band corresponding per forations on the edge portions of said photosensitive material. Such combination enables the registration also in the transversal direction as well as in the longitudinal direction, and is particularly useful in obtaining well-registered image in case of reproducing multicolered pattern by means of superposed printing method.

For the purpose of registration it is besides possible to employ other known means such as to realize registration in the longitudinal direction by defining the rotation of the drum 6 by optical mark reading and that V in the transversal direction by displacing the optical system.

Also provided in this example are a'corona discharge device 7 which applies corona discharge on the surface of photosensitive layer during the advancement of said photosensitive material thereby to obtain uniform surfacial charge thereon, a projecting optical system a for projecting the original image onto said photosensitive material to modulate said surfacial charge corresponding to said original image thereby forming latent image, and guide rollers 9 and lltl made for example of rubber for guiding said photosensitive material after exposure toward the developing section. Moistening of photosensitive material with highly insulative liquid prior to the contact with liquid developer which is effective for preventing the penetration of said liquid developer into said photosensitive material can be conveniently carried out between said rollers 9 and It).

Successively the continuous photosensitive web material is subjected to development.

In the developing section provided are guide rollers 11-16 for changing the advancing direction of said photosensitive material and at the same time acting as developing electrodes during advancement step. Said rollers can be shaped in a simple cylindrical drum as shown in FIG. 3, or shaped to have a central portion with smaller diameter as shown in FIG. 4 so as to prevent direct contact of said roller with image area. Said rollers can be composed for example of metal, metal with a surfacial insulative layer thereon, plastic material with electroconductively treated surface, electroconductive rubber etc., and the surface coarseness thereof is preferred not to exceed IOOS stipulated in JIS standard. Further provided are photosensitive material supporting drums l72O on which the continuous photosensitive web material is tightly wound with the rear surface toward said rollers. Said support drums can be composed of simple cylinder of uniform diameter, it is preferable to provide a spiral ditch of which spiral direction is inverted in the center of said drum in order to pull said photosensitive material toward the edge sides thereof upon rotation of said drums thereby preventing the formation of wrinkles when said photosensitive material is wound on said drums. Naturally such ditch should not be so large enough as to form concave portions on said photosensitive material resulting in uneven development. The characteristics of this invention capable of effecting development without any unevenness even under intermittent advancement of photosensitive material are realized by the arrangement of said support drums. More specially each rear side of image areas 33-40 represented by black portions is brought into intimate contact with one of the said support drums when said photosensitive material is in standstill. During the transfer from the exposure of a frame to the exposure of succeeding frame, the entire photosensitive material is advanced by the length of one frame thereby to displace the image area 33 to the position 34, the image area 3% to the position 35 and so on. The photosensitive material is brought to standstill again in this position and subjected to development during the exposure of succeeding frame. Thus, in this system, it is possible to effect the develop ment while the image areas are kept in correct facing relationship with developing electrodes irrespective of the length of the imagewise exposure. The image area 36 is not supported by a support drum and is guided in a space connecting the arrays of support drums. Said support drums 17-20 can be made of any underformable material not affecting the liquid developer such as metal, rubber, plastic, etc. In this section also provided are developer supply nozzles 21-25, and the liquid developer is taken out from an outlet 3t provided at the bottom of a developer tank 32 and cycled repeatedly to said nozzles 21-25 through a pump (not represented). In case of insufficient developed density due to the decrease of toner density, it is possible to replenish fresh developer in the course of circulation of said developer or to replace the course developer with fresh one. It is preferred that the supply of liquid developer from said nozzles is carried out exclusively while the photosensitive material is advanced and is interrupted while said material is brought to standstill. Said liquid developer is supplied into a space between the latent image surface of said photosensitive material supported on the support drums and the developing electrode plate mounted in facing relationship with said surface. In FIG. ll provided are developing electrode plates 26-30 at a constant distance from the latent image surface electrode plate. The developing electrode distance is not necessarily identical for all the developing electrodes 26-30. It is already found that, for realizing developing exactly corresponding to the charge density, said developing electrode distance should be relatively large at the initial stage of development and be gradually smaller toward the latter stages of development. In the example shown in FIG. 1, satisfactory result can be obtained by employing distances of 5, l, 0.5 and 0.3 mm for the developing electrodes 26-29, respectively. As regards the developing electrode 30, the developing electrode distance should be relatively large in order to prevent uneven developing since said distance is difficult to define on this electrode.

Guide rollers 41-43 for guiding the photosensitive material after development toward the rinse section are made for example of metal, rubber, plastic material etc., and are preferably shaped as shown in FIG. 5 or FIG. 6. A dancer roller 44 is provided in order to give the photosensitive material driven by the rollers 5 and 6 a determined tension over the exposure section and developing section thereby preventing slackening. Said roller is shaped as roller 4 shown in FIG. 5 to hold said photosensitive material between the flanges 50. A pair of pinch rollers 45 and 46 also for squeezing off the liquid developer remaining on thephotosensitive material consist preferably of smooth metal roller and rubber roller, respectively. The photosensitive material is-advanced by rotating either one of said rollers, for example the roller 46. Though .the photosensitive material is advanced intermittently in the exposure and developing sections, it is possible to rotate the pinch rollers 2, 3, 45 and 46 continuously and to absorb the aberration in the velocity of advancement by means of dancer rollers 4 and 44. Also it is naturally possible to advance said photosensitive material intermittently throughout from the unwinding drum to the drum. Also provided are supply nozzles 47-50 for rinse solution, which is contained in a rinse solution tank 51 and circulated repeatedly from an outlet provided at the bottom thereof to said nozzles through a pump (not represented). The photosensitive material washed and squeezed is taken up on a winding drum 53, which is preferably driven by means of a constant-tension motor.

As thus far explained, in case of forming images successively at a fixed interval on a continuous electrophotographic photosensitive web material, said material is advanced intermittently through the exposure section, and, when said material is brought to standstill in the liquid developer, a certain image area is placed in a defined position by means of a support drum and kept in facing relationship. with a developing electrode with an uniform distance thereto. Though uneven development is considerably suppressed due to the fact that the photosensitive material is supported on the periphery of support drum to facilitate to define the distance to the developing electrode, this is furthermore cancelled by the development through plural developing stages. Besides the supply of fresh liquid developer at the transfer from a developing stage to a succeeding one is effective for preventing uneven or insufficient development.

Although the example shown in FIG. 1 is provided with only four support drums, it is naturally possible to employ longer developing section by providing larger number of support drums in vertical direction or by utilizing plural units of developing sections shown in FIG. 1.

In FIG. 2 shown is another example with simplest structure with a horizontal array of support drums. This example is provided with support drums 201-203 simi lar to those employed in FIG. 11, guide rollers 204-207, developer supply nozzles 208-210 and developing electrodes 211-213. Image areas 214-217 are placed on the support drums to define the position thereof in the developing section, with the latent image surface thereof outwards to face said developing electrodes. Also in this example the advancement is always carried out by the distance between the succeeding frames so as to displace each image area to facing relationship with the succeeding developing electrode according to the spirit of this invention. Though the apparatus of this example is provided with only three support drums, it is naturally possible to employ larger number of support drums.

What is claimed is:

1. An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural, stationary developing electrodes disposed in said liquid developer which are larger in dimension than the latent image area formed on said photosensitive material and which are arranged along and outside the periphery of said support rollers so as to be in facing relationship with slight spacing therebetween with said continuous electrophotographic photosensitive web material to be wound on said support drums at least over the length of said latent image area with the rear side thereof towards the drums, a means for supplying liquid developer into the space between said developing electrodes and said'photosensitive material, and means for advancing said photosensitive material intermittently so as to bring all the latent image areas in the developing section into facing relationship with developing electrodes respectively when said photosensitive material is brought to standstill so the latent image areas may be subjected to simultaneous developing action.

2. An apparatus claimed in claim 1, wherein comprising rollers provided between said supporting drums for pressing the photosensitive material onto said support drums extending almost over the periphery thereof.

3. An apparatus claimed in claim 2 wherein said rollers have a central portion with smaller diameter.

4. An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural developing electrodes which are larger in dimension than the latent image area formed on said photosensitive material and which are arranged along the periphery of said support rollers so as to be in facing relationship with slight spacing therebetween with said continuous electrophotographic photosensitive web material to be wound on said support drums at least over the length of said latent image area with the rear side thereof towards the drums wherein said spacing is relatively large at the former support drum and relatively small at the latter support drum, a means for supplying liquid developer into the space between said developing electrodes and said photosensitive material, and advancing said photosensitive material intermittently so as to bring all the latent image areas in the developing section into facing relationship with developing electrodes respectively when said photosensitive material is brought to standstill. 

1. An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural, stationary developing electrodes disposed in said liquid developer which are larger in dimension than the latent image area formed on said photosensitive material and which are arranged along and outside the periphery of said support rollers so as to be in facing relationship with slight spacing therebetween with said continuous electrophotographic photosensitive web material to be wound on said support drums at least over the length of said latent image area with the rear side thereof towards the drums, a means for supplying liquid developer into the space between said developing electrodes and said photosensitive material, and means for advancing said photosensitive material intermittently so as to bring all the latent image areas in the developing section into facing relationship with developing electrodes respectively when said photosensitive material is brought to standstill so the latent image areas may be subjected to simultaneous developing action.
 2. An apparatus claimed in claim 1, wherein comprising rollers provided between said supporting drums for pressing the photosensitive material onto said support drums extending almost over the periphery thereof.
 3. An apparatus claimed in claim 2 wherein said rollers have a central portion with smaller diameter.
 4. An apparatus for developing continuous electrophotographic photosensitive web material which comprises plural support drums in an array in a container for liquid developer, plural developing electrodes which are larger in dimension than the latent image area formed on said photosensitive material and which are arranged along the periphery of said support rollers so as to be in facing relationship with slight spacing therebetween with said continuous electrophotographic photosensitive web material to be wound on said support drums at least over the length of said latent image area with the rear side thereof towards the drums wherein said spacing is relatively large at the former support drum and relatively small at the latter support drum, a means for supplying liquid developer into the space between said developing electrodes and said photosensitive material, and advancing said photosensitive material intermittently so as to bring all the latent image areas in the developing section into facing relationship with developing electrodes respectively when said photosensitive material is brought to standstill. 